UGT75L6 and UGT94E5 mediate sequential glucosylation of crocetin to crocin in Gardenia jasminoides

► Two glucosyltransferases mediate sequential glucosylation of apocarotenoid pigments. ► UGT75L6 catalyzes glucosyl ester formation from crocetin. ► UGT94E5 catalyzes glucosyl chain elongation leading to a final product crocin. Crocin is an apocarotenoid glycosyl ester accumulating in fruits of Gardenia jasminoides and used as a food coloring and nutraceutical. For the first time, the two glucosyltransferases UGT75L6 and UGT94E5 that sequentially mediate the final glucosylation steps in crocin biosynthesis in G. jasminoides have been identified and functionally characterized. UGT75L6 preferentially glucosylates the carboxyl group of crocetin yielding crocetin glucosyl esters, while UGT94E5 glucosylates the 6′ hydroxyl group of the glucose moiety of crocetin glucosyl esters. The expression pattern of neither UGT75L6 nor UGT94E5 correlated with the pattern of crocin accumulation in G. jasminoides.